The present invention pertains to improvements in the fluid pulsing system (liquid or gas) for centrifugal jigs. One specific type of liquid jig is disclosed in U.S. Pat. No. 4,279,741, issued July 21, 1981, which is hereby incorporated into this disclosure by reference. The general advantages and operational features of centrifugal jigs can be readily ascertained from the referenced patent. Depending upon the application of such jigs, either the heavy fraction or the light fraction separated by its operation might contain the values desired as an end product.
In the form of the centrifugal jig shown in FIG. 5 of the referenced U.S. patent, the rotating screen is associated with an exterior rotating hutch maintained full of liquid during jig operation. Fluid pulses are directed to the interior space of the fluid-filled hutch by a rotating supply valve in the form of a stationary head 62 provided with openings 64 that periodically register with similar openings 71 on a spinning rotor. When the openings 64 and 71 are not in registry with one another, flow of water in the head 62 is substantially stopped. The patent disclosure states that the complementary wall surfaces of the head and rotor will normally substantially nest and therefore very little seepage will be allowed into the hutch. However, by adjustment of shaft positions, steady seepage can be achieved to apply a continuous positive pressure to fluid within the hutch in addition to the positive pulsations required by the jig bed.
The present invention was developed to provide better definition to the jig pulses by producing more abrupt shock waves or pressure pulses that can be applied to the rotating hutch fluid. This is achieved by periodically directing continuously flowing pressurized fluid into the interior space of the hutch during rotation of the rotor without ever substantially obstructing the flow of the incoming pulse fluid. The fluid is alternately directed either to the interior space of the hutch or to the interior space of a surrounding shroud or enclosure. The present system makes efficient use of the dynamic energy contained within a constantly flowing supply of pressurized fluid by not obstructing movement of the incoming fluid that is periodically directed into the interior space of the hutch.